Alkali fusion of halogenated fatty acids



United States Patent Cheves T. Walling, Upper Montclair, N. 1., assignor to Lever Brothers Company, New York, N. Y.,' a corporation of Maine No Drawing. Application March.24,.1954 Serial No. 418,469

18 Claims. (Cl; 260-413) The present invention relates to" a process for preparing saturated fatty acids. More particularly, it? relates to a process for preparing a saturated fatty acid of relatively short chain length from a' fatty acid of longer chain. length. In brief the method of the invention comprises halogenating a higher fatty acid and then fusing. the. halogenated higher fatty acid with caustic alkali.

The higher fatty acids such as' stearic, oleic, p'almitic, and the like are often more readily available and less expensive than similar acids of lower molecular weight such as lauric, myristic, decanoic, etc. Since the lower fatty acids in many cases have several advantages and 1 uses not possessed by the higherfatty acids of the type mentioned above, it is obvious that a method by which a higher fatty acid can be converted to a fatty acid of shorter chain length is highly desirable.

The conversion of unsaturated fatty acids'to saturated fatty acids of lower molecular weight by fusion with alkali has been known for over a century, Varrentrap, Ann. 35, 210, (1840). This publication describes the reaction obtained when oleic acid is heated with sodium or potassium hydroxide at a temperature of about 300 C. While the overall major course of this reaction is" as follows:

CH3 (CH2) 7CH= CH CH2) 7COOH+2KOH- sium' iodide.

CH3 CH2 14COOK+CHaCOOK+H2 the mechanism of the reaction is obscure. In all 'instances, however, the final acid product of the reaction contains 2 carbon atoms less than the starting acid."

U. S. Patent No. 2,279,734 to Dreger'et al. contains examples of a reaction in which soaps of unsaturated fatty acids are prepared from saturated fatty acids. 'In the procedures exemplified in this patent a saturated fatty acid is submitted to chlorination. Thereafter thechlor'inated fatty acid is treated with sodium carbonate at an elevated temperature above the melting point of the anhydrous soaps formed and in an inert atmosphere; preferably steam, and in the substantial absence of. air and liquid water. The amount of sodium carbonate employed in the patent is sufiicient only to saponify and react with the chlorine atoms of the acid. The end products of the processes described in this patent'are mainly soaps of unsaturated fatty acids of approximately the same chain length as the starting acid.

It is a primary object of this invention" to provide a process for preparing fatty acids of relatively short chain length from saturated or unsaturated fatty acids of longer chain length.

The process of this invention comprises halogenating a saturated or unsaturated higher fatty acid and then fusing the halogenated fatty acid with caustic alkali. The r the halogenation reaction to yield products containing. on the average 2 to 12 carbon. atoms less than the starting acid. Examples of starting acids than can be used in the process of this invention are tridecoic acid,- myristic acid, palmitic acid, stearic acid, behenic acid, hyenic acid, oleic acid, linoleic acid, linolenic acid and ricinoleic acid.

In general, the manner in which the halogenation step of the present process is carried out is not critical and any one of a number of well-known procedures may be employed. As is well-known the halogenation of fatty acids is accelerated By light and 'other materials which act as carriers of halogen atoms. The halogenation of unsaturated fatty acids can be conventionally performed without the presence of a catalyst to introduce 2 halogen atoms for eachdoublebond in the acid molecule. The halogenated acid :can then be halogenated further, if desired, by the same methods hereinafter described for the halogenation of" saturated acids.

In the case of saturated fatty acids the halogenation is preferablyconducted at an elevated temperature in the presence of'li'ght or. other catalyst. The chlorination of a fatty acid, in addition to being accelerated by light, is also catalyzed by traces of iodine or red phosphorus. The bromination of fatty. acids canbe eifected readily by the use of a smalramdunt' of phosphorus tr'ichloride as a catalyst at'a temperature of about 65' to 70 C. Iodinated acids cannot beprepared by direct halogenation but can be obtained by metathesis" from .the brominated acids, for example, by reacting a brominated acid withpotas- While the invention contemplates the halogenation of 'a saturated or an unsaturated higher fatty acid with either bromine, chlorine or iodine, chlorina tion is actually preferred'for reasons of cost and ease of reaction. v

Halogenat'ion with bromine or chlorine, at least in the presence of light, is believed to be a free-radical chain reaction whichoccursmor'e or less at random alongthe fatty acid chain resulting in a mixture of products including unchlorinated acid and chlorinated acids-ofvarying degrees of chlorination. n the second step of the process, i. e., the fusion of'the chlorinated'acid with caustic alkali, certain criticali ties must be observed in order to obtain the desired results. The reaction which takes place in the alkali. fusion is believed to follow the following overall course using chlorinated palmitic acid and sodiumhydroxide for purposes of illustration: I

, +nH2+nNaC1+H2O wherein nequals' the number of atoms of chlorine inthe chlorinated fatty acid. As can-be observed from the equation for the reaction a certain minimum amount of caustic is required' Thus, if the number of halogen atoms in the chlorinated acid be taken as n, then, theoretically, there must be employed a minimum of approximately 2n+-1 moles of alkali. However, actual experiments have determined that a minimum of Zn moles: of alkali. gives a satisfactory produ t, The alkali employed must be sodium hydroxide oran alkaline compound possessing approximately the sa-me degree of alkalinity as sodium: hydroxide; Thus, sodium carbonate is too weak an alkali and cannotbe employed in the alkali fusion step of this process. However, alkalies sueh as potassium. hydroxide, calcium hydroxide and lithium hydroxide can be satisfactorily employed but sodium hydroxide is preferred because itis'less' expensive; The temperature of thealkali fusion is also important;

It has been found that the temperature must be iniexcess of 275 0., preferably at least 300 C.

In summary, the alkali fusion is performed by heating together the chlorinated fatty acid and the required min- 4 EXAMPLE 3 One molar quantities of stearic and palmitic acids were chlorinated as in Example 1. One mole of oleic acid was chlorinated as in Example 2. The chlorinated fatty acids thus obtained were fused with alkali (either KOH or NaOH) following the procedure of Example 1. The results of the individual experiments are presented in the following table:

TABLE 1 Alkali fusion of chlorinated acids Yield of Distilled Acids (Mole Ex- Atoms, P cent) Percent Percent ample Acid Cl Moles, Alkali Total Pet 0. Residue C10 C14 12 u 1 Triple Pressed 2. 0 4.80 KOH 0. 2 12. 7 l5. 2 7. 1 6. 6 41. 8 17. 5

stearic. 5 Palmitic 2. 0 6.10 KOH 17. 3 19. 9 6. 8 5. 3 49. 3 13. 3 2. 36 6.28 KOH 7. 2 20. 1 15. 5 12. 1 54. 9 16. 5 3. 0 6.14 KOH 0. 5 13. 9 17. 6 l2. 6 44. 6 30. 2 2. 0 6.30 NaOH 4. 2 16. 4 4. 9 6. 7 32. 2 23. 1

' All palmitic acid samples 90% technical material (Aliphat 6).

b Added as pellets, 1 mole initially, balance at about 150.

(In other experiments, alkali was added initially, usually as 50% aqueous solution.)

EXAMPLE 1 the increase in weight of the reaction vessel indicated that 2.0 chlorine atoms had been introduced for each mole of the fatty acid (approximately one hour).

One mole of the chlorinated palmitic acid was transferred to a stainless steel reactor equipped with a stirrer and a thermometer. There was added 4.25 moles of sodium hydroxide (50% aqueous solution). The mixture was then heated with continuous stirring to a temperature of 300 C. as rapidly as possible and maintained at that temperature for about one-half hour. The resulting product was isolated by pouring the cooled melt into water, acidifying and separating the mixed acids. The product was analyzed by fractional distillation and a total yield of 46.7 mole percent of saturated fatty acids were {ecovered of which 28.2% had chain lengths of C14 and ess.

EXAMPLE 2 One mole of oleic acid was placed in a glass reactor equipped with a stirrer and thermometer. Chlorine gas was passed through a fritted glass gas-dispersion tube into the acid at a temperature less than 100 C. in the absence of an appreciable amount of light. Chlorine addition was continued until the gain in weight of the reactor indicated that two chlorine atoms had become affixed by addition to the double bond of the oleic acid.

The chlorinated oleic acid was transferred to a stainless steel reactor equipped with a stirrer and thermometer. There was added 6.35 moles of potassium hydroxide (50% aqueous solution) and the mixture was heated as rapidly as possible with stirring to a temperature of 300325 C. After approximately one-half hour the reaction mass was cooled and the product was isolated by pouring the cooled melt into water, acidifying and separating the mixed acids. Fractional distillation of the product gave a total yield of 46.2 mole percent of saturated fatty acids of which 38.8% had chain lengths of C14 or less.

EXAMPLE 9 In order to verify the reaction obtained by alkali fusion of an unchlorinated fatty acid as reported in the literature, the following experiment was performed for comparison with Example 2.

One mole of oleic acid was mixed with 2.34 moles of potassium hydroxide 50% aqueous solution) and the mixture was heated as rapidly as possible to a temperature of 300-325 C. with stirring. After one-half hour the reaction products were separated as in Example 2. Fractional distillation of the product gave a total yield of 52.3 mole percent fatty acids of which the entire yield was C14 or above.

It is intended to cover all changes and modifications in the examples of this invention, herein given for purpose of disclosure, which do not constitute departure from the spirit and scope of the appended claims.

I claim:

1. A process which comprises halogenating a fatty acid having from 12 to 24 carbon atoms, fusing the resultant halogenated fatty acid with at least 2 moles of caustic alkali for each atom of halogen in the halogenated fatty acid to effect degradation of the halogenated fatty acid, and recovering saturated fatty acid of shorter chain length than the starting acid.

2. A process according to claim 1 in which the fusion with caustic alkali is carried out at a temperature of at least 275 C.

3. A process which comprises halogenating a fatty acid having from 12 to 24 carbon atoms, fusing the resultant halogenated fatty acid with at least 2 moles of caustic alkali for each atom of halogen in the halogenated fatty acid to effect degradation of the halogenated fatty acid, and recovering saturated fatty acids having from 2 to 12 carbon atoms less than the starting acid.

4. A process according to claim 3 in which the fusion with caustic alkali is carried out at a temperature of at least 275 C.

5. A process according to claim 3 in which the starting fatty acid is palmitic acid.

6. A process according to claim 3 in which the starting fatty acid is oleic acid.

7. A process according to claim 3 in which the starting fatty acid is stearic acid.

8. A process according to claim 3 in which the halogenation is chlorination.

9. A process'according to claim 3 in which the caustic alkali is sodium hydroxide.

10. A process according to claim 3 in which the caustic alkali is potassium hydroxide.

11. A process which comprises fusing a halogenated fatty acid having from 12 to 24 carbon atoms with at least 2 moles of caustic alkali for each atom of halogen in said halogenated fatty acid to effect degradation of the halogenated fatty acid, and recovering saturated fatty acids having from 2 to 12 carbon atoms less than said halogenated fatty acid.

12. A process according to claim 11 in which the fusion is carried out at a temperature of at least 275' C.

13. A process according to claim 11 in which the halogenated fatty acid is a chlorinated fatty acid.

14. A process according to claim 11 in which the halogenated fatty acid is halogenated palmitic acid.

15. A process according to claim 11 in which the halogenated fatty acid is halogenated oleic acid.

References Cited in the file of this patent UNITED STATES PATENTS 1,959,478 Keller May 22, 1934 2,279,734 Dreger et a1. Apr. 14, 1942 2,481,356 Segessemann Sept. 6, 1949 2,625,558 Logan Ian. 13, 1953 OTHER REFERENCES Synthetic Organic Chemistry, by Wagner and Zook, copyright 1953, p. 434, section 272. 

1. A PROCESS WHICH COMPRISES HALOGENATING A FATTY ACID HAVING FROM 12 TO 24 CARBON ATOMS, FUSING THE RESULTANT HALOGENATED FATTY ACID WITH AT LEAST 2 MOLES OF CAUSTIC ALKALI FOR EACH ATOM OF HALOGEN IN THE HALOGENATED FATTY ACID TO EFFECT DEGRADATION OF THE HALOGENATED FATTY ACID, AND RECOVERING SATURATED FATTY ACID OF SHORTER CHAIN LENGTH THAN THE STARTING ACID.
 2. A PROCESS ACCORDING TO CLAIM 1 IN WHICH THE FUSION WITH CAUSTIC ALKALI IS CARRIED OUT AT A TEMPERATURE OF AT LEAST 275* C. 